at89c51cc02ua-tdsum ATMEL Corporation, at89c51cc02ua-tdsum Datasheet - Page 21

• Manufacturer Part Number: at89c51cc02ua-tdsum
• Description: At89c51cc02, T89c51cc02 Enhanced 8-bit Microcontroller With Can Controller And Flash
• Manufacturer: ATMEL Corporation

During a Normal
Operation (Warm Reset)
Watchdog Reset
4126L–CAN–01/08
Table 14. Minimum Reset Capacitor for a 15k Pull-down Resistor
Note:
Reset pin must be maintained for at least 2 machine cycles (24 oscillator clock periods)
to apply a reset sequence during normal operation. The number of clock periods is
mode independent (X2 or X1).
A 1K resistor must be added in series with the capacitor to allow the use of watchdog
reset pulse output on the RST pin or when an external power-supply supervisor is used.
Figure 6 shows the reset circuitry when a capacitor is used.
Figure 6. Reset Circuitry for a Watchdog Configuration
Figure 7 shows the reset circuitry when an external reset circuit is used.
Figure 7. Reset Circuitry Example Using an External Reset Circuit
oscrst/vddrst
External reset
circuit
20ms
These values assume VDD starts from 0v to the nominal value. If the time between two
on/off sequences is too fast, the power-supply decoupling capacitors may not be fully
discharged, leading to a bad reset sequence.
5ms
VDD
Crst
VDD
1k
2.7µF
10µF
1ms
RST
RST pin
1k
Rrst
RST pin
To other on-board circuitry
10ms
4.7µF
15µF
Reset input circuitry
AT/T89C51CC02
Rrst
To other on-board circuitry
Internal reset
watchdog
Reset input circuitry
Internal reset
watchdog
100ms
47µF
47µF
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